1. Activate the Plugin for Multisite Network
First things first, once you added the plugin to your website, you have to “Network activate” it. In order to do so, please go to My Sites > Network Admin > Plugins and click “Network activate” link.

2. Configure what Blogs you Would Like to Allow for Cross-Posting (Optional)
If you skip this step, the plugin is going to use the 5 sub-sites from your Network ordered by their ID.
Otherwise if you have hundreds of sub-sites in your Network, it is better to choose which ones you would like to allow for crossposting. In order to do so, please go to Network Admin > Sites, the select a website you would like to configure, click “Edit” link first, then select “Crosspost” tab.

3. Select the Sub-sites When Creating a Post
In case you’re using Gutenberg editor:

In case you’re using Classic Editor:

4. Sync the Content Between Posts
Once you published a post on multiple website in your Network, you can deactivate the checkboxes, if you don’t, you posts will continue to sync!
This is how it would work: